The nonagenarian was found dead half naked on her bed next to a sex toy in Aveiro, 50 miles south of Porto, Portugal, reported the Mirror.
A neighbour in his late 40 was arrested after DNA analysis of semen recovered from the scene. He was later released on bail after autopsy results confirmed she died from asphyxia thought to have taken place during a sex game that spiralled out of control.
The victim was described as being "very active" despite her age and said the neighbour often went round her house to do odd jobs.
Police say there was no sign of a forced entry and nothing had been taken from the house.